Except for the carrying of passenger baggage, the capacity of the lower cargo hold of an aircraft is often poorly utilized. This is especially true for the standard-width body, short to medium range airplanes. These planes typically do not have automated cargo-handling systems and the airport short turnaround time required for these planes is frequently insufficient to permit any significant amount of nonbaggage cargo to be manually loaded and unloaded.
In larger, wide-bodied planes, cargo is shipped as a unit-load commonly in standardized, rigid containers that are loaded into the lower cargo hold with power operated equipment. In one typical arrangement, the floor of the hold is equipped with powered and unpowered rollers or balls that bear against the underside of the containers to move them horizontally into, out of, and along the cargo hold. Similar containers have not been widely utilized in standard-width body aircraft. One reason for this is that such containers would have to be reduced in size to fit within the smaller cargo holds of these planes and, thus, the containers would have a high tare weight in comparison to the cargo weight.
In another type of aircraft cargo system, longitudinal rows of rollers support the container for movement along the fuselage. An elongate powered dolly rides in a narrow track extending along the center of the cargo hold floor. A relatively small bearing plate is carried on the end of the dolly. The bearing plate is raised to bear against the underside of the container and lowered by inflating and deflating an underlying airbag. An example of this type of cargo system is disclosed by U.S. Pat. No. 3,756,544.
In a further aircraft cargo system, the rigid cargo containers are moved longitudinally through the fuselage by a powered carriage mechanism. The carriage mechanism includes a pair of lifting arms that slide under the container to support the container above the floor as the container is being moved. An example of this type of cargo system is disclosed by U.S. Pat. No. 3,861,841.
The rigid cargo containers that are in current use are typically owned by the airlines and packed and unpacked by airline personnel. Airfreight rates probably could be reduced if containers were owned, packed, and unpacked by the shipper. As a consequence, low-cost, lightweight shipping containers are now being developed for ownership by the shipper. These containers could be constructed from cardboard, low-density plastic, and would be of sufficient structural integrity to be reused only a limited number of times. This type of container construction would be especially advantageous for smaller containers employed in conjunction with standard-width body aircraft; however, this type of container could not be used until systems are developed for rapidly loading and unloading the containers into and out of aircraft. Because of the relatively low structural integrity of these types of containers, the powered roller or powered ball systems currently in service for transferring the rigid containers of the wider bodied aircraft could not be employed. The same is true for the cargo transfer system disclosed in the above-noted U.S. Pat. No. 3,756,544.
Another consideration in developing a powered transfer system for loading and unloading unit-loads from standard-width body aircraft is that the standard lower cargo hold openings of such aircraft typically do not extend the full height of the hold. As a consequence, if the unit-load enters and exits the cargo hold on a horizontal transfer device as in the systems disclosed in the above-mentioned U.S. Pat. Nos. 3,756,544 and 3,861,541, the height of the load would be limited by the height of the hold opening, and thus, a significant volume of the hold would not be utilized.
Accordingly, it is a principal object of the present invention to provide a powered system for loading and unloading unit-loads of various configurations (for instance, in the form of a lightweight, low structural integrity container or in the form of a number of small packages bound together on a standard commercial pallet or slipsheet) into and out of the lower cargo hold of a standard-width body aircraft rapidly and with a minimum amount of manpower.
It is a particular object of the present invention to provide powered transfer system for loading onto and unloading from aircraft, unit-loads having a height larger than the vertical height of the cargo hold opening.
It is another particular object of the present invention to provide a powered system for loading and unloading lightweight, low structural integrity containers and other unit-loads on existing standard-width body aircraft without requiring any major structural alterations to the aircraft.
To achieve these objectives, it is desirable to provide a cargo transfer system that is integrated into the aircraft and capable of receiving low structural integrity unit-loads through the standard cargo hold opening in the side of the fuselage and then shifting the direction of travel of the unit-loads to move along the length of the cargo hold. In the past, several types of conveyor transfer devices have been developed for changing the direction of movement of items being transported on the conveyors. For instance, U.S. Pat. Nos. 3,104,004, 3,221,754 and 3,321,063 disclose devices utilizing rather small lugs carried by endless chains arranged transversely to the conveyor on which the container or object is being transported. The lugs push against the lower edge of a container or other object being transported to force the container sideways off of the conveyor and onto another conveyor. The container or other object must have sufficient structural integrity to withstand the pushing force of the lugs, which probably would not be the case for cardboard or a similar limited-duty container with which the present invention is contemplated for use.
Another known manner of shifting the direction of travel of an object moving along a conveyor system is by rotating the conveyor about a vertical axis, thereby changing the direction of operation of the conveyor itself. Examples of such systems are disclosed by U.S. Pat. Nos. 2,021,251; 2,732,067; and 3,100,039.
In a further type of conveyor system, articles are transferred from a first conveyor to a perpendicularly arranged second conveyor by a plunger that pushes against the side of the object moving along the first conveyor, thereby sliding the object onto the second conveyor. It will be appreciated that for heavy objects, such as aircraft freight containers or other unit-load packaging, the container or packaging must have sufficient structural integrity to withstand the force of the plunger and the resisting frictional force acting between the first conveyor and the bottom of the container or packaging. An example of this type of conveyor system is disclosed by U.S. Pat. No. 3,469,887.
In an additional known type of conveyor system, articles are routed in a particular direction by a transfer station composed of one or more belts disposed transversely to a plurality of elongate rollers to move articles in a direction perpendicular to the direction in which the rollers are adapted to move articles. The rollers and the belts are vertically movable relative to each other so that either the rollers or belts function as a moving surface for transferring articles arriving at the transfer station, depending on the desired direction of travel. Examples of this type of conveyor system are disclosed in U.S. Pat. Nos. 3,680,677 and 3,756,374. A similar conveyor mechanism is disclosed in U.S. Pat. No. 1,472,697 wherein the rollers and conveyor are disposed at separate fixed levels of a frame structure. The entire frame structure is vertically movable to position either the belt or the rollers in coplanar relationship with associated conveyors that carry articles to and away from the moving frame structure in different directions, depending on the elevation of the frame structure.
In another type of conveyor system, the transfer station is located at the intersection of three conveyor belts, with two of the belts in longitudinal alignment on opposite sides of the transfer station and the third belt disposed perpendicular to the first two belts. The transfer station itself includes an endless belt in line with the first two belts. Articles moving along the first belt can be transferred to the aligned second belt by the transfer station belt. To change the direction of movement of the article from the first belt to the transverse, third belt, the transfer station belt is lowered and then air discharged up through exhaust holes formed in the surface of the transfer station, in theory to lift the article above the top surface of the transfer station. The article is then pushed transversely onto the third belt by a plunger positioned on the side of the transfer station opposite the third belt. An example of this type of conveyor system is disclosed in U.S. Pat. No. 3,822,777.